Description

Our solar photovoltaic
installation converts sunlight to 240 volt AC electricity. Any power generated
in excess of what we use is delivered to the electric company (PG&E) for
distribution to others. Our electric meter records the net power (consumed minus
generated). If we generate more than we consume, the meter runs backwards and we
receive a credit. The process is called "Net Metering". We have a time of day use
meter. We pay 8 cents a kilowatt/hour from 6 pm to 10 noon and 32
cents a KW/h from noon to 6 pm. If the sun is out, this will mean we will
be selling power to PG&E at 32 cents a KW/h from noon to 6 pm (which is
about peak for the system in the summer) and will be selling power at 8 cents a
KW/h at other times.

The installation consists of (36) 165 watt Sharp photovoltaic panels and two
SMA Sunny Boy 2500 watt inverters. Due to loses and inefficiencies, the
total installation is rated 5000 watts or 5 Kilowatts. I designed my
own mounting system made from Unistrut aluminum channel and custom made aluminum
brackets. By using aluminum for the mounting hardware, I was able to keep
the weight of the installed system lower and avoid galvanic action due to dissimilar
metals (the frames of the PV panels are aluminum). I chose to have the
panels separated a little in between each panel and between each row. This
was done mainly for cooling in the summer and ease of maintenance. It is
very important to remember that all the components on the DC side of the system
be rated for DC. Sometimes these items can be hard to find.

The Sharp PV panels come with USE-2 wire with integral MultiContact connectors.
This is a UL listed wiring system. The panels just plug together. We
did have to make sure that none of the wires were exposed, since the voltage in
them can exceed 400 volts DC. We did this by making sure the wires were up
underneath the panels. I had to add some raceway for the wires to get
between sections of panels on bank 2 where they were separated by the
skylights. The inspector initially had a problem with the wiring method
until I showed him the UL listing of the panels and MultiContact
connectors. He also was going to turn down the inverter hook up because he
considered them a separately derived system. They are not since there is
no neutral connection and the inverters need AC power to operate and they are
directly connected to my main panel, they can not generate electricity if there
is not PG&E voltage present. We called his boss and his boss agreed
that I was correct. The inspector signed the permit and left with a little
of his ego bruised.

The system has no moving parts and no
batteries. The only maintenance is a once a year check of the mounting brackets
and the electrical connections. The estimated life of the system is
more than 25 years. We hope that what we are doing will (1) pay for itself in a
reasonable period of time (at the current rates we are guessing between 6 and 8
years), (2) be some small help to alleviate California's
power problems and our country's dependence on oil, and (3) encourage others to
do the same, (4) allow us to use our house as a showcase for selling PV
installations through the company I work for, Clark Electric.

My union, the IBEW Local 332, partnered with the NPCP (see the links below)
to make a group purchased of the photovoltaic panels and inverters.
This allowed us to get the items at wholesale prices. The goal of
this partnership is to train our unionís members in the installation of PV
systems.To this end I can say it
is working.I learned a lot about
PV systems and their installation though my own installation (enough to know at
least more than the inspector).

If you live in the Santa Clara County (CA) and are interested in a solar
electric system like mine, please contact me, Vince Endter or Virgil Clark at
Clark Electric, 408-988-4358.

Results

There is a program available on the web for calculating system performance
called PV Watts.
I used this program to calculate how much my system should output. For the
first 30 days of operation (December 12 to Jan 11), my system output 298 kilowatt hours of
electricity. This is about 20 kilowatt hours less than I was
expecting. Most of the 20 kilowatts hour loss came from shading on my
system. I have observed that with 12% of the system shaded, the output
drops by 50%. It is very important to keep shade from your system. My shade is coming from my neighbors
trees. The worst tree is two houses
away. I am hoping as summer comes and the sun is higher in the sky, this
tree will no longer shade my system. There is still one palm tree that
will shade my panels for about 2 hours a day. There is a law in California
(the
Warren-Alquist act section 25980) that say once you install a system, no one
can build or plant anything that will shade your system. This law does not
apply to existing conditions when your system is installed. The first 14
days of operation it rained or was overcast every day. I have had only
three cloud free days in the first 28 days of operation.

I had calculated that we should generate 20 kWh around the shortest day
of the year and 40 kWh on the longest day. On March 18th, a few days
before the equinox, we generated 30kWh. It looks like I am right on with
my calculations.

Interesting cloud effect: I noticed on days with cumulous clouds, when
the sun would appear, the system out put jumped from 3800 watts to 5000 watts, a
31% increase. I called Sharp solar and asked about this. The cause
of this they said was something they called the cloud effect. It only
happens with cumulous clouds. When the sun appears next to a cumulous
cloud, the cloud focuses the light from the sun increasing the suns intensity.

The effect of dust on performance. We went 4 weeks without any
rain. I noticed a film of dust had covered the panels. I hosed off
the panels to wash away the dust. After cleaning off the dust, I had a 7%
increase in output.

Daily Output

Monthly Output

Monthly Bill

Milestones

Jan 16, 2003 Daily output exceeded 20 kWh for the first time (20.6).
Jan 25, 2003 Total output exceeds 500 kWh
February 1, 2003 Power output exceeds 4000 watts for the first time (4100
watts).
February 2, 2003 Fist day we generated more electricity than we used.
February 23, 2003 Total output exceeds 1000 kWh.March 25, 2003 Total energy output exceeds our usage since system
installation.Total system output from 12/12/02 to 08/302008 - 62566 kWh.
Pounds of CO2 abated - 91346
This is an equivalent to the energy (if used to generate electricity) in 5213 gallons of gasoline.

Photos

Select each image by clicking on the picture.

12/12/02 - The completed installation

The end
bracket and strut support for the end of a row of panels. One can
see the 1/4" bolt and cone nut with which the bracket is connected.

This is another view of the end bracket. One can
also see the support for the Unistrut.

The custom bracket that is placed between two
panels.

There are two
rows of (9) panels each that feed each inverter. These two rows are
paralleled before the inverter. This requires each row to have it's
own 10A DC rated fuse.

A view inside
the combiner box showing the fuse and fuse holder installation.

Unistrut supports for bank 2.

Unistrut supports for bank 1.

View of bank 1. 18 PV panels..

View of bank 2. 18 panels. Notice the extra
work to install the panels in between the skylights and the different
widths of the roof.

These are the two SMA Sunny Boy 2500U inverters.
Also in the picture are the two 600V DC disconnects and the sub panel
above the inverters that I used to combine both inverter outputs so they
could be wired to a single disconnect required by PG&E.

The disconnect required by PG&E. It must be
within sight of and no more than 10' from the meter. I have a
disagreement with PG$E about the necessity of this switch since the
inverter can not generate electricity without PG&E voltage present.
The requirement for this disconnect added about $1000 to the installation
cost of the system.